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Old 11-15-06, 01:03 PM   #1
wcr007
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Default X process saturates the CPU when Xinerama (SLS) enabled

Hi,

We are experiencing a problem where the X process saturates the CPU when we run a java application (using JRE v1.4 and v1.5) in Xinerama (Single Logical Screen) mode under Xorg v.6.9.

We are using four LCD monitors with two PCIe Nvidia Quadro FX3500 graphics cards along with the latest driver (version 1.0-9629) but can reproduce the problem with the last six versions of the driver.

I should mention that the problem seems to go away if we use TwinView. For our purposes however, we need to run in SLS mode using Xinerama.

Also, we can reproduce this particular problem under the following Linux distributions:
- Suse Enterprise Linux Desktop v.10
- Redhat Enterprise WS v.4.0
- Fedora Core 5
- Debian Sarge

At this point, we suspect the driver may be contributing to the problem.
Has anybody experienced something similar?
Can anybody share their thoughts on this?

Please see the attached nvidia bug report log file.
Thanks,

Walter
Attached Files
File Type: gz nvidia-bug-report.log.gz (41.6 KB, 112 views)
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Old 11-15-06, 01:13 PM   #2
netllama
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

Specifically which Java application is this that triggers the problem?
How are you determining that the CPU is saturated?
Does this reproduce with the Java2D Demo that ships with the JDK?

Thanks,
Lonni
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Old 11-15-06, 02:44 PM   #3
wcr007
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

Hi,

Thanks for your response. The Java application which I was referring to is a meteorological tool which was written in-house. When we run this application, we notice that the X process (as seen through 'top') saturates one of our four CPU cores.

When we run in TwinView, we notice that the X process doesn't exhibit the behaviour described above.
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Old 11-15-06, 03:10 PM   #4
netllama
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

Is this behavior specific to your app, or is it evident with any other Java apps? I'd be happy to look into this if you could provide me with a means of reproducing it.

Thanks,
Lonni
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Old 11-16-06, 01:13 PM   #5
kafshar
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

Hi,

I work alongside Walter and thought I could add the following to the discussion:

Since yesterday, we've set up a similar system to the one above with two PCIx Matrox graphics cards and could NOT reproduce the problems we are seeing with the PCIe Nvidia Quadro FX3500s!

We believe that the problems we're seeing when running our in-house application (which runs multiple animation windows) may be related to a behavior we've noticed when we run glxgears:

A single instance of glxgears produces framerates in the range of 27000 FPS. However, starting another instance of glxgears on the same card, lowers the FPS for both instances to around 750 FPS

This is a monumental drop and we think that it is related to the same problem we're seeing in our application (even though we're not seeing the X process taking over one CPU core).

We've conducted the multiple glxgears test on older Nvidia graphics cards and noticed that the FPS drops by only half.

Any thoughts?

Thanks,
Kaveh
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Old 11-16-06, 01:21 PM   #6
netllama
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

glxgears performance is very rarely a reliable measurement of anything, and is usually not linear in nature due to the numerous bottlenecks that impact glxgears performance.
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Old 11-16-06, 01:42 PM   #7
Linuxhippy
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

@wcr007:

Could you please try the Java2D-Demo shipped with the JDK version of java?
Simply start java -jar demo/jfc/Java2D/Java2D.jar and let the animation run.

lg Clemens
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Old 11-21-06, 10:27 AM   #8
wcr007
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

Bonjour,

we tried to reproduce it with Java2D-Demo, but could not.

Thanks for the suggestion.
--
Walter
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Old 11-21-06, 10:52 AM   #9
netllama
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Default Re: X process saturates the CPU when Xinerama (SLS) enabled

So you're stating that this only reproduces with glxgears & your internal application (and nothing else)?
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